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arXiv 0903.1870astro-ph.GAastro-ph.HE
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最年轻的银河系超新星遗迹G1 .9+0.3的X射线光谱变化

X-ray Spectral Variations in the Youngest Galactic Supernova Remnant G1.9+0.3

S. P. Reynolds, K. J. Borkowski, D. A. Green, U. Hwang, I. Harrus, R. Petre

摘要:

最年轻的银河系超新星遗迹(SNR)G1.9+0.3的发现让我们看到了以前从未观察到的SNR演化阶段。我们分析了50 KS钱德拉观测,特别是关于光谱变化。非常高的柱密度($N_H \sim 6 \times 10^{22}$ cm $^{-2}$)意味着尘埃散射是重要的,我们使用一个简单的散射模型在我们的光谱分析。G1.9+0.3的积分X射线能谱由指数截止的幂律电子分布的同步辐射很好地描述。使用我们测量的无线电通量,包括散射效应,我们发现一个滚降频率为$5.4 (3.0, 10.2) \times 10^{17}$ Hz($h ν_{\rm roll} = 2.2$ keV)。在两区域模型中包括散射给出了超过2倍的较低的ν_roll值。将G1.9+0.3划分为6个区域,我们发现在壳层明亮的SE和NW边缘有一个光谱最硬(最高ν_roll)的系统模式。当你绕着贝壳或进入内部时,它们会变陡。在壳层明亮部分之外的延伸具有最硬的光谱。我们解释的冲击加速性能的依赖关系的冲击速度和一个相当均匀的上游磁场之间的夹角$θ_{\rm Bn}$的结果。这种解释可能需要Ia型事件。如果电子加速受到同步加速器损耗的限制,则光谱变化需要加速率与磁场强度无关。

英文摘要:

The discovery of the youngest Galactic supernova remnant (SNR) G1.9+0.3 has allowed a look at a stage of SNR evolution never before observed. We analyze the 50 ks Chandra observation with particular regard to spectral variations. The very high column density ($N_H \sim 6 \times 10^{22}$ cm$^{-2}$) implies that dust scattering is important, and we use a simple scattering model in our spectral analysis. The integrated X-ray spectrum of G1.9+0.3 is well described by synchrotron emission from a power-law electron distribution with an exponential cutoff. Using our measured radio flux and including scattering effects, we find a rolloff frequency of $5.4 (3.0, 10.2) \times 10^{17}$ Hz ($h ν_{\rm roll} = 2.2$ keV). Including scattering in a two-region model gives lower values of ν_roll by over a factor of 2. Dividing G1.9+0.3 into six regions, we find a systematic pattern in which spectra are hardest (highest ν_roll) in the bright SE and NW limbs of the shell. They steepen as one moves around the shell or into the interior. The extensions beyond the bright parts of the shell have the hardest spectra of all. We interpret the results in terms of dependence of shock acceleration properties on the obliquity angle $θ_{\rm Bn}$ between the shock velocity and a fairly uniform upstream magnetic field. This interpretation probably requires a Type Ia event. If electron acceleration is limited by synchrotron losses, the spectral variations require obliquity-dependence of the acceleration rate independent of the magnetic-field strength.

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